GREGORY, Mark David (14 Belford Avenue, Devon Park, South Australia 5008, AU)
1. A protective helmet formed wholly or partially from thermoplastic material having an appropriate level of transparency.
2. A protective helmet according to Claim 1, formed wholly from the thermoplastic material.
3. A protective helmet according to Claim 1, the front portion of which is formed from the thermoplastic material.
4. A protective helmet according to Claim 1 having a brim, and wherein all of the brim, or the front portion of the brim, is formed from the thermoplastic material.
5. A protective helmet according to any one of Claims 1 to 4, wherein the thermoplastic material is selected from polycarbonates, polymethyl methacrylates, acrylonitrile butadiene styrenes (ABS) and polysulfones.
6. A protective helmet according to any one of Claims 1 to S, wherein the thermoplastic material is tinted.
7. A protective helmet according to any one of Claims 1 to 6, substantially as described herein.
 This invention relates to safety or protective helmets of the type normally referred to as hard hats.
BACKGROUND TO THE INVENTION
 There are many examples of hard hats or similar protective headgear to prevent workplace injury.
 However, these hard hats have a significant deficiency in that components such as the brim obscure the wearer's vision of overhead hazards.
 In addition, when looking upwards, the wearer's eyes may be affected by sun glare or the wearer may be blinded by the sun.
 In order to overcome this deficiency without compromising the strength and impact resistance of the hard hat, part or all of the hard hat, its brim or any component of the hard hat which would otherwise restrict the wearer's vision (particularly the wearer's vision of overhead objects) is formed from transparent thermoplastic material.
SUMMARY OF THE INVENTION
 In a first aspect, the present invention provides a protective helmet formed wholly or partially from thermoplastic material having an appropriate level of transparency. The appropriate level of transparency will depend on circumstances such as the wearer's working environment, but should be sufficient to allow the wearer to recognise falling objects of sufficient size to be of danger, and other overhead hazards.
 In particular, part or all of the protective helmet, its brim or any component of the protective helmet is formed from thermoplastic material having an appropriate level of transparency.
 The thermoplafrtic material™»y be tinted to reduce glare or blindness from the sun, and to provide protection from the effects of the sun's rays (such as protection from sunburn).  Preferably, the protective safety helmets will be made to comply with Australian and/or US Standards for hard hats.
BRIEF DESCRIPTION OF THE DRAWINGS
 The invention will be described in more detail with reference to the attached drawings, wherein:
Fig. 1 is a perspective view of a typical ha d hat to be manufactured according to the present invention; and
Fig. 2 is a perspective view of a different version of the hard hat
DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS OF THE INVENTION
 The safety or protective helmet (hard hat) will now be described in terms of preferred embodiments, which are illustrative, but not restrictive, of the present invention.
 The helmet (hard hat) 10 is wholly or partially formed from thermoplastic material having an appropriate level of transparency. For added strength, and to ensure that there are no potentially weakened joints or fracture lines where thermoplastic material is joined to other materials, the helmet 11 itself and its brim 12 or visor will, in a preferred embodiment, be formed (e.g. by injection moulding) solely from that thermoplastic material. However, accessories and components such as head straps 13 and chin straps (for adjusting the fit of the helmet) can be formed from other materials. Also, there may be situations where it is appropriate to manufacture part only of the helmet or its brim from the thermoplastic material (particularly if the technology is available to form an impact-resistant weld or joint between the thermoplastic material and the material forming the remainder of the helmet). In that case, the back portion (for example, back half) of the helmet may be made of standard material, with the front portion (for example, front half) manufactured from the clear (transparent) thermoplastic material. In another version, it may (for example) be only the brim, or even just the front portion of the brim, of the helmet that is manufactured from the thermoplastic material.
 The thermoplastic material of the helmet (hard hat) may be tinted to provide some protection from the sun's rays and to reduce glare. A clear (untinted) version may be preferable for use at night or in dark conditions (for example, when working within a building, tunnel or mine).  The thermoplastic materials are selected for their strength and impact resistance, and because many have the required level of transparency. Examples of thermoplastic materials that can be used include (but are not limited to):
• Polymethyl methacrylates (PMMA; acrylic)
• Acrylonitrile butadiene styrenes (ABS)
 Polycarbonates are easily worked, moulded and thermoformed. In particular, polycarbonates derived from bisphenol A (BPA) are very durable and have high impact- resistance. However, they are easily scratched, so a scratch resistant coating may be applied. Polycarbonates are, in general, highly transparent to visible light, and may have better light transmission characteristics than many kinds of glass.
 Polymethyl methacrylates (PMMA; acrylic) have similar properties to polycarbonates, and are generally cheaper (but not as strong).
 Polysulfones are tough, rigid, high-strength, impact resistant and transparent Their strength can be further increased by incorporating glass fibres for reinforcement. A disadvantage is that they tend to be relatively expensive.
 Acrylonitrile butadiene styrenes (ABS) are common thermoplastic copolymers made by polymerizing styrene and acrylonitrile in the presence of polybutadiene, The proportions can vary between 15 to 35% acrylonitrile, 5 to 30% butadiene and 40 to 60% styrene. They tend to be high-strength, tough and rigid, with good impact resistance. The impact resistance can be increased by increasing the proportion of polybutadiene in the copolymer. Their strength can be further increased by incorporating glass fibres for reinforcement.
[0001 ] m order to facilitate better understanding of the invention, the present invention has been described in terms of preferred embodiments, and with regard to the particular elements and/or features described or depicted therein. It should however be appreciated that various modifications can be made without departing from the principles of the invention. Therefore, the invention should be understood to include all such modifications within its scope.  For instance, various thermoplastic materials have been specified by way of example only, and other thermoplastic materials having the required properties of strength, rigidity, impact resistance and transparency (light transmission) may be used instead.